Berenstain Bears No Girls Allowed by Stan and Jan Berenstain

Sister bear wanted to be like her big brother and his friends, so she started joining their games of marble and climbing the tree. She soon grew older and ran faster then them, beat them in playing marble, and climbing the tree. The brother and his friends built a clubhouse in the thicket, but no girls were allowed in the house. Her papa and her friends built a no boys allowed clubhouse. Eventually they got along and they let the boys in the girl house and the boys let the girls in the boy house.